| one publication added to basket [24698] | Equatorial western Atlantic Ocean circulation changes linked to the Heinrich events: deep-sea sediment evidence from the Amazon Fan
Maslin, M. (1998). Equatorial western Atlantic Ocean circulation changes linked to the Heinrich events: deep-sea sediment evidence from the Amazon Fan, in: Cramp, A. et al. Geological evolution of ocean basins: results from the Ocean Drilling Program. Geological Society Special Publication, 131: pp. 111-127. https://dx.doi.org/10.1144/GSL.SP.1998.131.01.09
In: Cramp, A. et al. (1998). Geological evolution of ocean basins: Results from the Ocean Drilling Program. Geological Society Special Publication, 131. Geological Society: London. ISBN 1-86239-003-7. XI, 323 pp., more
In: Hartley, A.J. et al. (Ed.) Geological Society Special Publication. Geological Society of London: Oxford; London; Edinburgh; Boston, Mass.; Carlton, Vic.. ISSN 0305-8719; e-ISSN 2041-4927, more
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| Keywords |
Aquatic communities > Plankton
Deglaciation
Foraminifera
Motion > Water motion > Circulation > Water circulation > Ocean circulation
Sedimentation > Glacial sedimentation
Water > Deep water
South America, Amazon R. [Marine Regions]
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| Abstract |
The Amazon Fan is an excellent area to obtain climatic records of the last glacial-interglacial cycle. Glacial sedimentation rates ranging from 1 to over 50 m ka−1 provide an opportunity to obtain marine records approaching the resolution of the Greenland ice cores. Ocean Drilling Program Leg 155 Sites 932 and 933 from the Eastern Middle Amazon Fan complex have been studied at a resolution of 50 cm (100–400 years). The identification of palaeomagnetic excursions, distinctive patterns in the palaeomagnetic remanence intensity records and AMS 14C dates have provided an age framework for both Sites 932 and 933. However, due to extensive reworking in the Site 933 records, it was only possible to construct a detailed age model for Site 932. Planktonic foraminiferal stable oxygen and carbon isotope records of six species were obtained for both sites.The planktonic foraminiferal carbon isotope records of both Sites 932 and 933 show a distinct negative deviation during Termination I (13–15 calendar ka). We suggest this could have been caused by an increase in the sediment discharge of the Amazon River because of the deglaciation of the Andes and/or the release of significant quantities of gas hydrates as large parts of the Amazon Fan sediment column failed because of increased sea level. Positive δO deviations are also observed in the Site 932 records which seem to be coeval with the Heinrich events. It is suggested that the enhanced ice-rafting in the North Atlantic during the Heinrich events increased the latitudinal thermal gradient and thus the zonal component of the wind system. This reduced the northward penetration of the Inter-Tropical Convergence Zone, curtailing the cross-equatorial export of the North Brazilian Coastal Current (NBCC) and resulting in a permanent NBCC-reroflection. This increased the surface water salinity of the Amazon Fan and thus led to the observed positive δO deviations. |
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